laravel中selectRaw查询

laravel中如何使用selectRaw和group by

```
selectRaw('id+tag_id as id_tag_id')->selectRaw("concat(id,'---',tag_id) as cnt")->where('tag_id',$id)->get();
echo "

";

print_r($data->toArray());

$data = Table::select(\DB::raw('DATE(created_at) as year, COUNT(*) as amount'))->where('tag_id',$id)->groupBy(\DB::raw('date(created_at)'))->first();

echo "
";

print_r($data->toArray());

?>

```